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af988bf866
## Summary
With this PR, we emit a diagnostic for this case where
previously didn't:
```py
from typing import Literal
def f(m: int, n: Literal[-1, 0, 1]):
# error: [division-by-zero] "Cannot divide object of type `int` by zero"
return m / n
```
## Test Plan
New Markdown test
2.1 KiB
2.1 KiB
Binary operations on union types
Binary operations on union types are only available if they are supported for all possible combinations of types:
def f1(i: int, u: int | None):
# error: [unsupported-operator] "Operator `+` is unsupported between objects of type `int` and `int | None`"
reveal_type(i + u) # revealed: Unknown
# error: [unsupported-operator] "Operator `+` is unsupported between objects of type `int | None` and `int`"
reveal_type(u + i) # revealed: Unknown
int can be added to int, and str can be added to str, but expressions of type int | str
cannot be added, because that would require addition of int and str or vice versa:
def f2(i: int, s: str, int_or_str: int | str):
i + i
s + s
# error: [unsupported-operator] "Operator `+` is unsupported between objects of type `int | str` and `int | str`"
reveal_type(int_or_str + int_or_str) # revealed: Unknown
However, if an operation is supported for all possible combinations, the result will be a union of the possible outcomes:
from typing import Literal
def f3(two_or_three: Literal[2, 3], a_or_b: Literal["a", "b"]):
reveal_type(two_or_three + two_or_three) # revealed: Literal[4, 5, 6]
reveal_type(two_or_three**two_or_three) # revealed: Literal[4, 8, 9, 27]
reveal_type(a_or_b + a_or_b) # revealed: Literal["aa", "ab", "ba", "bb"]
reveal_type(two_or_three * a_or_b) # revealed: Literal["aa", "bb", "aaa", "bbb"]
We treat a type annotation of float as a union of int and float, so union handling is relevant
here:
def f4(x: float, y: float):
reveal_type(x + y) # revealed: int | float
reveal_type(x - y) # revealed: int | float
reveal_type(x * y) # revealed: int | float
reveal_type(x / y) # revealed: int | float
reveal_type(x // y) # revealed: int | float
reveal_type(x % y) # revealed: int | float
If any of the union elements leads to a division by zero, we will report an error:
def f5(m: int, n: Literal[-1, 0, 1]):
# error: [division-by-zero] "Cannot divide object of type `int` by zero"
return m / n